Rocket Lab & NASA launch CAPSTONE to the Moon

written by Mihir Neal June 27, 2022

Rocket Lab has launched the CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) satellite to the Moon. It’s the first official mission of NASA’s Artemis program that is seeking to permanently return humans to the surface of our nearest astronomical body.

Launching onboard the Electron rocket, liftoff occurred at 5:55 AM EDT (09:55 UTC) on Tuesday, June 28, from Launch Complex 1B at Rocket Lab’s launch facility on Māhia Peninsula, New Zealand. This mission made Electron the smallest rocket to launch a payload toward the Moon and the first lunar flight to lift off from New Zealand.

Rocket Lab did not recover the first stage on this mission, hence the Electron launch vehicle supporting this mission flew in a standard configuration without any recovery hardware.

The second stage of the Electron placed the payload in an initial low Earth orbit. To propel the 25 kg (55 lbs) CubeSat to the moon, Rocket Lab’s Lunar Photon — optimized especially for Lunar missions — will give the payload the extra thrust needed to get it to the Moon.

Powered by green-hypergolic propellants, its onboard Hypercurie engine will place the CAPSTONE satellite on a ballistic lunar transfer orbit. Unlike the free return trajectory utilized during Apollo lunar missions of the 1960s and 70s, this fuel-efficient ballistic lunar transfer makes it possible to deploy CAPSTONE to such a distant orbit using a small launch vehicle.

Once in lunar vicinity, the CAPSTONE satellite will use its onboard propulsion systems to place itself in a Near Rectilinear Halo Orbit around the Moon.

CAPSTONE Payload

CAPSTONE is a CubeSat developed by the Terran Orbital Corporation and managed by NASA’s Small Spacecraft Technology Program within the agency’s Space Technology Mission Directorate. 

This is the first mission to launch that directly supports NASA’s Artemis program, which plans to return humans to the Moon and advance humanity’s ways to Mars. As such, CAPSTONE will be the first spacecraft to enter the Near Rectilinear Halo Orbit (NRHO) around the Moon.

An NRHO is a one-week, highly eccentric orbit that works with a balancing point in the gravities of the Earth and Moon. This makes the orbit ideal for crewed missions onboard the Gateway space station, NASA’s Orion spacecraft, and/or SpaceX’s lunar variant of Starship as it provides crews routine access to the polar lunar landing sites that are the Artemis program’s targets.

Apart from access to the surface and fuel efficiency, an NRHO will allow scientists to take advantage of the deep space environment for radiation experiments to gather a better understanding of the potential impacts of space weather on people and instruments. Most importantly, an NRHO trajectory also has a continuous line of sight, or “view”, of Earth, resulting in uninterrupted communications between the spacecraft and home.

This differs from the Apollo missions which periodically lost communications with the Earth when they passed behind the Moon.

The NRHO orbit will also bring CAPSTONE within 1,600 kilometers of one lunar pole on its near pass and 70,000 kilometers from the other pole at its peak every seven days, requiring less propulsion capability for spacecraft flying to and from the Moon’s surface than other orbits would allow.

CAPSTONE is planned to reside in this orbit for at least six months to characterize the properties of this unique orbit.

The satellite will also validate the power and the propulsion requirements to maintain this orbit as predicted by NASA’s models, thereby reducing logistical uncertainties for Orion and Starship operations. CAPSTONE will also demonstrate the reliability of spacecraft-to-spacecraft navigation systems as well as its communications capabilities with Earth, something which will be used extensively during the crewed Artemis missions by the Orion spacecraft and Starship Human Landing System (HLS).

CAPSTONE will accomplish these objectives by using its onboard secondary payload flight computer and radio to perform calculations to determine its position in the orbit. This will be done using data taken by NASA’s Lunar Reconnaissance Orbiter (LRO) as a reference point.

The CAPSTONE payload in Rocket Lab’s integration facility at LC-1. (Credit: Rocket Lab)

This peer-to-peer navigation system is named Cislunar Autonomous Positioning System, developed by the owner and main operator of the mission: Advanced Space. 

This technology will be used to evaluate CAPSTONE’s autonomous navigation software. If successful, this software will allow future spacecraft to determine their location without having to rely exclusively on tracking from Earth.

Overall, these are part of CAPSTONE’s six mission objectives:

• verify the characteristics of a cis-lunar Near Rectilinear Halo Orbit
• demonstrate entering and maintaining this unique orbit
• lay a foundation for commercial support of future lunar operations
• demonstrate spacecraft-to-spacecraft navigation
• demonstrate one-way ranging technique using Deep Space Network signals and a Chip Scale Atomic Clock
• gain experience with small, dedicated launches of CubeSats beyond low-Earth orbit, to the Moon, and beyond. 

Launch Timeline

Final preparations for launch began six hours before liftoff with the closure of the road to the launch site. At T-4 hours, Electron was raised to the vertical position. After pad connection checkouts, fueling of the rocket with RP-1 kerosene began, with liquid oxygen flowing to the rocket at T-2 hours at the same time safety zones were activated for the marine space around the launch track.

At T-30 minutes, airspace closures took effect for launch. This was followed at T-18 minutes by the GO / NO GO poll. 

Proceeding from that point, the next major event occurred at T-2 minutes when the launch auto-sequence began and Electron’s onboard computers took control of the countdown.

At T-2 seconds, Electron’s 9 Rutherford engines ignited and built up to full thrust as engine health checks were carried out before the vehicle was released for flight at T0.

Electron then pitched and rolled onto an easterly trajectory to achieve the needed initial low-Earth orbit inclination for the mission. At T+2 minutes 41 seconds, the first stage engines shut down, followed by stage separation. At T+2 minutes 51 seconds, Electron’s second stage vacuum-optimized Rutherford engine ignited, with fairings separating just 27 seconds later.

At T+6 minutes 36 seconds, the initial set of batteries on the second stage were depleted and “hot swapped” with unused batteries on the stage. At this time, the spent batteries (Battery A and B) were jettisoned to reduce mass on the stage as it continued to climb to orbit. 

At T+9 minutes, Electron achieved a low orbit of 165 kilometers. Over the next five days, Photon’s HyperCurie engine will perform a series of orbit-raising maneuvers from this initial parking orbit roughly once every 24 hours.

The Lunar Photon spacecraft before integrating the CAPSTONE payload. (Credit: Rocket Lab)

The Photon will perform burns every day to increase the stage’s velocity and increase the eccentricity of the orbit as it continues its way to the Moon. On the sixth day, HyperCurie will burn for the last time, accelerating the payload to 39,500 kilometers per hour and into a trans-lunar injection trajectory that will take CAPSTONE from Earth to the Moon.

Twenty minutes after the Photon’s last burn is complete, CAPSTONE will be released from the Photon satellite bus.

Commanded by teams at the Advanced Space mission operations center, CAPSTONE will then perform a series of planned trajectory correction maneuvers using its onboard low-energy propulsion systems. 

Overall, the final Photon burn will send CAPSTONE 1.3 million kilometers from Earth, more than three times the distance to the Moon before the Earth-Moon system’s gravity pulls and tugs it back towards the Moon. 

CAPSTONE will arrive in its NRHO of the Moon four months after launch.

(Lead photo: Electron lifts off with CAPSTONE. Credit: NASA)